In general, a molding cycle in an injection molding includes a mold clamping process of combining separated molds to form a cavity, a filling process of filling a molten resin by using an injection section having a screw, a pressure-keeping process, a cooling process of cooling the molten resin, a mold unclamping process of separating the molds, and a molded-item take-out process. Of these molding processes, the filling, pressure keeping, and cooling operations performed by the injection section (injection operation) have effects on quality of the molded item or productivity. Therefore, for the injection molding device that automatically performs the molding processes as described above, it is important how to decide control conditions such as the amount of the control and the control timing of the injection operations.
For example, an injection molding device shown in Patent Literature 1 includes an injection unit that fills a molten resin in a cavity, and a mold internal pressure sensor that detects the pressure in the cavity. From the beginning of filling the resin until the mold internal pressure reaches a predetermined value, the injection pressure of the injection unit is controlled in such a manner that a forward movement velocity of an injection screw correspond to a predetermined velocity waveform pattern (normal filling process). After the mold internal pressure reaches the predetermined value, the injection pressure of the injection unit is controlled in such a manner that the mold internal pressure correspond to the predetermined pressure waveform pattern (mold internal pressure control process). With these controls, the molten resin is injected at a high speed, and the mold internal pressure is totally decreased while evenly keeping a pressure distribution in the cavity to prevent the occurrence of a weld mark or warping in the molded item.
Additionally, an injection molding device shown in Patent Literature 2 employs a heating-cooling molding, which is a type of injection molding methods. That is, this injection molding device has a temperature adjustment unit that adjusts the temperature of a mold. The injection molding device coordinates control of molding processes and control of a mold temperature in such a manner that a mold temperature adjustment process is performed in accordance with the progress of the molding process.
Patent Literature 1: Japanese Patent No. 4127339 (FIG. 6)
Patent Literature 2: Japanese Unexamined Patent Application, First Publication No. 2006-110905